Emphyasis will be placed upon two major problems: 1)The 100K protein will be purifed and characterized, chemically and immunologically, to investigate its role in the development of hexons. 2) The fiber mutant, H5tsl42, will be further employed to study virion assembly. Attention will be directed toward: a) obtaining conclusive evidence that the empty capsid is the virion precursor: and b) studying the mechanisms and control of the processing of proteins pVI, pVII, and pVIII during assembly.